Reaction injection molding (RIM) is a versatile process by which elastomeric and thermoset parts can be fabricated. The RIM process involves high pressure impingement mixing of a polyisocyanate stream (A-side) and an active-hydrogen containing isocyanate-reactive stream (B-side) followed by immediate injection into the closed mold. The primary appeal of this process lies in its inherently high productivity. One factor which limits productivity, however, is the necessity to spray the molds with external mold release prior to each injection. This is a time-consuming task and often has a negative environmental impact. This difficulty can be overcome by the incorporation of an internal release agent into the formulation via one of the two streams to significantly increase the number of molding cycles which can be accomplished between mold release sprayings.
The use of metallic soaps as release agents has been known for a long time. Zinc stearate, in particular, is known to be soluble in aliphatic amines, such as the polyether polyamines and ethylenediamine-initiated polyols. This is the basis for its use as an internal mold release (IMR) agent in RIM. If zinc stearate is simply dispersed as a fine powder in polyol blends, it does not dissolve and does not act as a release agent. Various patents teach that zinc soaps can be compatibilized or dissolved in polyol blends with amines, enamines, ketimines or salts of amidines or guanidines, and that excellent releasability of the subsequent RIM parts will result.
While the IMR approach is commercially applied, there remain significant shortcomings to the currently available IMR systems. The amine-solubilized metallic soaps, which are most commonly used in this application, have been implicated in reactivity and/or physical property deficiencies for the RIM elastomers in which they are used. Furthermore, the high melting points and limited solubilities of the metallic soaps make them prone to precipitation in the RIM processing equipment, necessitating replacement of the piping regularly.
Salts formed by the neutralization of tertiary amines with fatty acids have been disclosed (U.S. Pat. No. 4,098,731) as IMR for integral-skin urethane foams. Similarly, salts of primary amines are disclosed in U.S. Pat. No. 3,726,952.
U.S. Pat. No. 4,220,727 discloses aralkyl quaternary ammonium salts as release agents. All of the examples are chloride salts containing at least one "phenyl stearyl" group.
U.S. Pat. No. 4,519,965 discloses an internal mold release agent mixture comprising a zinc carboxylate and a compatibilizer for the zinc carboxylate which is a nitrogen-containing, isocyanate reactive, acyclic compound or a nitrogen-containing, isocyanate-reactive polymer.
U.S. Pat. No. 4,753,966 discloses mold release compositions which are liquid at room temperature comprising a zinc carboxyl ate and at least one organic compound of the formula H.sub.2 N-(CH.sub.2).sub.m -X where X denotes a defined organic group containing nitrogen and/or oxygen.
U.S. Pat. No. 4,766,172 discloses mold release compositions which are liquid at room temperature comprising a zinc carboxylate and at least one defined organic compound containing tertiary nitrogen atoms.
U.S. Pat. No. 4,764,537 discloses internal mold release agents comprising at least one ketimine, aldimine, enimine, cyclic Schiff base, an organic carboxylic acid having 8 to 24 carbon atoms and, optionally, a carboxylic acid.
U.S. Pat. No. 4,886,838 discloses a mold release agent comprising a zinc carboxylate and a specific salt of an amidine-group containing compound.
U.S. Pat. No. 4,897,428 discloses an internal mold release agent comprising zinc oleate or zinc laurate and a specific fatty amine derivative.
U.S. Pat. No. 5,002,999 discloses an internal mold release composition comprising (a) a zinc carboxylate which is zinc stearate, zinc laurate or zinc oleate and (b) a compatibilizer comprising a dispersion of polyurea and/or a polyhydrazodicarbonamide in an organic compound containing at least one hydroxyl group, in an amount sufficient to solubilize the zinc carboxylate.
U.S. Pat. No. 4,585,803 discloses internal mold release compositions comprising a tertiary amine compound and a metal salt of a carboxylic acid, the acid containing at least one lipophilic group which renders it incompatible with an active hydrogen containing composition.
WO 84/03288 discloses an active hydrogen-containing composition which provides mold release properties to a molded article prepared from the composition and a polyisocyanate, the composition comprising (A) a metal salt of an organic carboxylic acid, (B) an active hydrogen-containing material having a plurality of either one or a combination of primary amine and secondary amine groups and optionally hydroxyl and/or thiol groups, the portion of component (B) containing primary amine groups and/or secondary amine groups and component (A) being present in a weight ratio of at least 2:1; and optionally, (C) an organic material containing a carboxylic acid group wherein at least one of components A, B or C contains at least one lipophilic group.
U.S. Pat. No. 4,040,992 discloses the use of N-hydroxyalkyl quaternary ammonium carboxylate salts as catalysts in the production of polyisocyanurates and polyurethanes. Among the exemplary preferred catalysts are N-hydroxypropyl trimethyl ammonium salts of carboxylic acids such as those of formic and acetic acids and of fatty acids such as hexanoic and octanoic acids and the like.
U.S. Pat. Nos. 3,892,687; 3,993,652 and 4,116,879 disclose the use of N-hydroxyalkyl quaternary ammonium phenolate salts as catalysts in the production of polyisocyanurates and polyurethanes.
U.S. patent application Ser. No. 07/992,404 filed 16 Dec. 1992 discloses an internal mold release composition consisting essentially of (1) the reaction product of a mixture of a carboxylic acid, a tertiary amine, and a reactive epoxide and (2) a carboxy functional siloxane as an additive to the active hydrogen-containing B-side composition for reaction with a polyisocyanate-containing A-side composition to make a polyurethane or polyurethaneurea elastomer.